(1) Field of the Invention
The present invention relates to the detection of the position of a movable member relative to a reference point and particularly to the sensing and subsequent generation of signals commensurate with the movements of a control member. More specifically, this invention is directed to position sensing systems wherein there is no direct mechanical connection between the member, the position of which is to be monitored, and the elements which sense and provide signals indicative of the position of that member. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
There are numerous situations where the position or orientation of a movable member relative to a point or axis must be sensed. Such sensing may be for the purpose of providing position or orientation information or it may be for the purpose of generating signals which are employed in the exercise of control over a remotely located apparatus. For example, it may be mandatory or desirable to detect and indicate an out-of-level condition of a platform, typically for the purpose of actuating devices which return the platform to the desired level condition. As a further example, there are numerous cases where it is desirable to provide a controller, capable of one-hand operation, for generating control signals for devices which adjust the position of a member about two or three axes. The latter example is exemplified by cranes and other similiar pieces of construction equipment which are controlled by means of a "joystick".
Perhaps the most common method of sensing the position of a movable member relative to a pair of mutually orthoginal axes is to couple the wiper arms of potentiometers to the movable member. While this technique may be suitable for applications such as electronic games, where a high degree of reliability is not required, the use of wiping-type contacts is certainly not conducive to long trouble-free operation. While it has been suggested that wiping contacts may be eliminated through the use of LVDT systems, wherein a magnetic core moves with the member of interest relative to fixed coils, such magnetic position sensors are characterized by sensitivity to noise. This is particularly disadvantageous in the case of a position sensing system which will be used in an environment where other electrical machinery may be operating. A further disadvantage incident to the use of a moving core resides in the fact that, in order to provide an output signal of usable magnitude, specially shaped cores must be formed at considerable expense.